Couplers which release a development accelerator (DARC) have been described. They are added to silver halide emulsions in order to achieve an increase in speed or contrast brought about by the increased image development caused by the image-wise release of the development accelerator Typically, these couplers release a hydrazide nucleator which is activated by oxidized color developing agent and hydroxyl ions.
UK Application No. 9716554.2, filed Aug. 6, 1997, discloses a new fogging photographic processing solution for a reversal process comprising a 1-phenyl-3-pyrazolidinone derivative and a bi-nucleophilic agent.